Idle problems, did some troubleshooting, still got questions!

[RatedR]

I'm helping another SR swap owner get his car running and the damn thing is just a pain. I've rewired the ECU wiring harness and it went from no spark to cranks and starts, but dies. I've eliminated the throttle sensor as a potential problem, the car will stay running if you feather the throttle. The only thing I can think of would be either the MAF or timing issues. The idle control didn't affect the motor's response, I've tried adjusting it.

My question is, can you use the DOHC MAF sensor for an SR? I was looking through the SR parts list and it said SOHC for the MAF. Also, what would cause this to die out? I'm having the owner take the intercooler plumbing off to check for dirt/clogs and I'm thinking the CAS maybe installed incorrectly. If you guys need more info to help diagnose, let me know. I'm pretty good w/ a KA, but this is the first SR motor I've actually laid a hand on.

[Blown240sx]

Yes you can use the DOHC MAF cause we used it on one of my buddies SR. Just match the wiring color up and throw it on should work fine.

[S13FASTBACKSR]

also sounds like its possibly a bad ecu..once you put in a new maf if that does not solve the problem try that..also maybe try cleaning the maf before you go and spend money on another one..no harm done there might save you some time and money

[RatedR]

What do you mean by matching up the colors?Is there something you have to rewire to make it work?

Also, the owner pulled off the piping and found oil in the piping of the blow-off valve, I'm thinking the turbine might be leaking.... Any other thoughts?

[S13FASTBACKSR]

yes turbo could be bad but that would be a whole seperate problem i believe. it wouldnt cause the problems you are having..by matching up the colors he means make sure you have the 12v wire coming from your harness to the 12v pin of your maf. same for 5v and ground

[RatedR]

If I remember correctly, the farthest wire was white, middle was black, lastly is white/black. I'm not sure if that's right, but I remember having MAF issues with my KA. When I pulled off the MAF connection, it killed the motor. Almost similar to the way the SR is dying, but the motor can stay running w/ some throttle input. I don't think the timing can cause this because the motor starts right up everytime, but it just dies after idling for 15 - 20 secs.

[S13FASTBACKSR]

yes that is correct..did you have any problems with the ka maf? it shouldnt die when you unplug it..if you are going to try another maf make sure its good...if it cant hold idle then i would try cleaning your iacv or also it is possible you have a bad computer.

[RatedR]

Yeah, the KA MAF was working well. The IACV valve is located on the driverside on the head right?

[S13FASTBACKSR]

iacv is located on the bottom of the intake manifold, which is the passenger side. if you look straight down between the 2nd and 3rd runners of your intake manifold IIRC (maybe 3rd and 4th) you will see a phillips screw facing straight up between the runners..the screw sits on a somewhat square metal box looking thing thats your iacv. its very noticable. you will see it right away once you start looking..if you need to know how to clean it just post back up and we'll help you out

[RatedR]

Okay, I know what you're talking about. Its the box that controls the idle. I've tried adjusting the screw and it didn't change anything. Should I just take it off and clean it with some carb cleaner? The other thing I had to do for this guy was rewire his entire harness. He bought an engine set w/ a bad harness, it was cracked and it split into 3 pieces. He got another clip and I rewired everything from the other wiring harness clip to the good one. I'm very confident I did everything right, we had wiring diagrams and I pretty much know my S#it when it comes to electrical. I just never messed w/ an SR before so its kinda hard diagnosing a motor you've never seen run right in the first place.

[S13FASTBACKSR]

well to clean it you just remove the screw and hit inside with carb cleaner. you never have to take anything off other than the screw..you can also spray compressed air in there if you have an air compressor and tap it with a piece of wood and hammer to loosen up carbon..but looking back to your first post and seeing the problems you are having i realize you say it went from no spark to crank and now start but dies...well if you can tell me if it starts everytime now that would help...does it start everytime without trouble? if so have you drove it around to see if it has any other problems other than bad idle? if its just bad idle its possible that it is the iacv..the no spark issue may have just been because it was a new swap and the engine was sitting awhile and needed some time to get going..if you arent running rich at all i would think its not your maf. let us know if it starts everytime and if you have any other problems besides bad idle.

[RatedR]

The motor starts right up everytime, just wont hold idle and dies. That's why I thought it isn't a timing problem. We haven't tried driving it around for fear of what could happen to the motor under load. The no spark problem came from the wiring, after I redid the harness, the spark came on and the motor starts up everytime. Just having the idle problem and dying out. So you really think its just the IACV? I don't see the car running rich.....

[S13FASTBACKSR]

if you think its timing then just have you buddy sit it the car and start it up and then feather the gas only as little as needed though to keep it running while you adjust the cas back and forth to see if it helps. if not then yes clean the iacv. use carb cleaner and hit it with compressed air. and like i said put a piece of wood to it and tap the wood with a hammer...if this doesnt help you may need a whole new one..also did you say you checked thoroughly for vaccuum leaks? if the problem is a vaccuum leak it sounds like you just have a small hole in one of the hoses. try this stuff and let us know

[RatedR]

Let me just get things in order, for an idle issue, the following are the usual suspects:

1)MAF2)IACV3)CAS

Now since the car starts everytime but just doesn't hold idle, I'll take this as a drivability problem, not a starting problem. It could still be timing cause of the CAS. Last time I checked, the timing with the motor running is on the TDC (Second one from the left to right). Now to my understanding, it should be 15 degrees right? That's the second one from the right to the left, if what I read online is correct.Did I miss anything?

[S13FASTBACKSR]

if your timing is still at tdc ( yes second mark from the left going to the right, usually its painted a different color) then that is most likely your problem. that is waaay off. yes it should be 15degress (yes second mark from the right going to the left.) if your maf was bad you would be running rich. fix your timing if that doesnt do it (but i think it will if its really at tdc right now) then clean your iacv

[RatedR]

Alright, I just came back from the guy's house and no luck. I've triple checked the timing, reset the CAS, adjusted it while giving some throttle input (Second timing mark from the left) and NOTHING. I've also clean out the screw and the IACV, but I wasn't sure where you wanted me to put the wood to hit, so I skipped that. I checked his ECU, its a J4 for a redtop and doesnt have the diagnostic screw in the back to pull the codes from. Could that possibly be the problem? Should the ECU be an E5 or a J4 for a redtop?

Oh, and I noticed a small vacuum nipple coming from under the throttle body. Does that go anywhere? Everything else is plugged into something, just that nipple.

PS - would it help to take a video clip and post it?

[S13FASTBACKSR]

ok i searched but didnt find the exact answer. the redtop uses a 62 or 63 ecu. but I THINK the s13 blacktop uses these too but can also use an E5. i dont know why a s13 blacktop would be able to use and E5 and a redtop wouldnt. you are going to have to research this. also you may just need a whole new iacv

[RatedR]

So it doesn't matter that the ECU doesn't have a diagnostic screw? How about the vacuum nipple and the video? Any input on those?

[S13FASTBACKSR]

oh sorry didnt see the part about the video and vaccuum nipple first of all the screw is used for nothing but to check codes so you are ok unless you need to check codes. second of all is the nipple plugged? if not thats your problem

[RatedR]

I've tried plugging the nipple w/ my finger wearing nitrile gloves while firing the motor, and no difference. The owner was looking around online and found that if the ECU is the wrong kind, it could make the motor fire on only 1 cylinder. Any truth behind that?

[xpicer]

yes because u need a j4 harness to go wih a j4 ecu unless you swap the pins on the harness